This invention relates to a display device with a plurality of light-emitting devices mounted at desired locations on a display surface of a multi-layered structure of the display device, and to a multi-layered structure and light-emitting devices for such display device.
In his Japanese Unexamined UM Publication No. SHO 60-189084 U published on Dec. 14, 1985, Y. Nagai discloses an electric light board including light-emitting diodes each having a shorter electrode plug and a longer electrode plug of which a portion is insulated. The light-emitting diodes are pushed into a board including a plurality of soft, electrically conductive sheets and a plurality of soft, electrically insulating sheets. Y. Nagai does not show materials of the soft, electrically conductive sheets.
K. Kato et al., in their Japanese Unexamined UM Publication No. SHO 49-5374 U published on Jan. 17, 1974, disclose a position indicating device including light-emitting diodes each having a shorter electrode and a longer electrode with an insulating layer thereon, and a display plate including two conductive thin sheets with an insulating thin sheet interposed between the two conductive sheets. The conductive sheets are formed of metal, or rubber or synthetic resin with minute particles of conductive material mixed therein.
In Japanese Unexamined Patent Publication No. SHO 47-22093 A published on Oct. 6, 1972, S. Wada shows a display device including a laminate sheet of two or three conductive layers of metal or conductive resin and two or three insulating layers of soft synthetic resin, and light-emitting diodes each having longer and shorter contact needles coated with insulating material except the respective end portions thereof. The contact needles of the light-emitting diodes are pushed into the laminate sheet so as to contact the associated conductive layers.
With the above-described arrangements of the prior art display devices, electrical contact between the light-emitting diodes and the conductive layers is insufficient and unstable. In some cases, some diodes may lose sufficient electrical contact, which makes the diodes unable to emit light, or contact portions may be oxidized as time passes, so that power cannot be supplied to the diodes.
An object of the present invention is to provide a display device having a display surface, and a light-emitting device which can be mounted at substantially any desired position on the display surface. Another object of the present invention is to provide a conductive layer for a multi-layered structure for such display device, which can provide stable conductive contact with leads of a light-emitting device to be pushed into the multi-layered structure. A still further object of the present invention is to provide a display device in which a light-emitting device to be energized can be selected.
A display device according to the present invention includes a multi-layered structure and a plurality of light-emitting devices mounted on a display surface of the multi-layered structure. The multi-layered structure includes successively stacked first, second and third insulating layers with the first layer on the display surface side, a first conductive layer sandwiched between the first and second insulating layers, and a second conductive layer sandwiched between the second and third insulating layers. Each of the first, second and third insulating layers is formed of such a material that a needle or the like can be stuck into it. Also, each of the first and second conductive layers is a layer into which a needle or the like can be stuck and which contains fibers. Each of the light-emitting devices has a longer lead and a shorter lead, which are stuck into the multi-layered structure through the display surface at substantially any desired location. When stuck, the longer lead extends through the first and second insulating layers and the first conductive layer at least into the second conductive layer and contacts the second conductive layer. An insulating coating or covering is provided on the longer lead at a portion thereof which contacts the first conductive layer in the multi-layered structure when the longer lead is stuck into the multi-layered structure. This insulating coating insulates the longer lead from the first conductive layer. The shorter lead extends through the first insulating layer at least into the first conductive layer and contacts the first conductive layer when it is stuck into the multi-layered structure.
The first, second and third insulating layers may be of insulating foamed plastic.
At least one of the first and second conductive layers may be separated into plural sections of desired shapes.
The longer lead of each light-emitting device may be provided with an insulating coating on at least a part of a proximal portion thereof having a length equal to that of the shorter lead. The insulating coating has its distal end narrowed down.
The first and second conductive layers include woven or non-woven fabric. The fabric can establish stable electric contact between the leads of the light-emitting devices and the conductor layers.